The invention relates to a quadrature to counter control pulse converters and in particular the method and apparatus to perform the conversion in a basic number of steps with minimum logic modules and increased resolution.
The term quadrature is known in the prior art to describe two signals generated from a sensor or configuration of sensors usually on a rotating member that have a 90 degree phase shift relationship to each other. The quadrature pulse train is used to provide direction and count information to counters or position indicators and controls. Raw, unprocessed quadrature pulses can be used directly into Up/Down counters by applying one channel to the count input and the other to the Up/Down control input. However, if any degree of vibration or rotary oscillation is present, the edge of the drive member may move back and forth across the count sensor several times. This causes the sensing of additional erroneous counts called "jitter".
There are known techniques to eliminate the effects of jitter by determining direction of count through storing of the state of the quadrature signals and comparing this stored data to the state of the quadrature signals after a transition. There are also known techniques for increasing resolution by a factor of two by operating on both edges of one of channels of the quadrature pulse train, and also by a factor of four by operating on both edges of both channels of the quadrature pulse train. What is needed is a technique for eliminating jitter and increasing resolution without the complexity of the storage of the quadrature pulse train which requires considerable digital logic components.